1. Field of the Invention
The present invention relates to a package structure of LED device, and more particular to a package structure of high-strength and airtight multi-layer array type LED device capable of completely blocking vapor and moisture, being durable in use, and maintaining the performance of optical component in long term.
2. The Prior Arts
The light-emitting theory of LED takes advantage of the intrinsic properties of semiconductors, which is different from the theory of electric discharging, heat and light-emitting of an incandescent light tube. Because light is emitted when electric current forward flowed across the PN junction of a semiconductor, the LED is also called cold light. The LED has the features of high durability, long service life, light-weight, low power consumption, and being free of toxic substances like mercury, and thereby it can be widely used in the industry of luminance equipment, and LEDs are often arranged in an array and often used in such as electric bulletin board or traffic sign.
Please refer to Taiwanese Patent No. M393044 titled in “Optical lens with fluorescent layer applicable in a LED packaging structure”. Please refer to FIG. 1, which is a cross section view showing an optical lens with a fluorescent layer applied in a LED packaging structure. The optical lens with a fluorescent layer applied in a LED packaging structure includes a substrate 1a, a package member 2a, lead frames 3a, an optical lens 4a, and a lens cover 5a. The substrate 1a is disposed at the bottommost layer of the package structure, wherein each surface of the substrate 1a is a flat and smooth surface, and the periphery of the substrate 1a is covered and fastened by the package member 2a. The inner wall surface of the package member 2a is installed with a light reflector 6a, and the package member 2a also covers and fastens the lead frames 3a, wherein each surface of the lead frames 3a is also a flat and smooth surface.
The light reflector 6a is installed with the optical lens 4a and the lens cover 5a, wherein the lens cover 5a covers the optical lens 4a, and the lens cover 5a is fastened on top of the light reflector 6a with an adhesion means, such that the lens cover 5a is mounted in the package member 2a, thereby firmly fastening the lens cover 5a in the package member 2a and on the light reflector 6a. 
However, one disadvantage of conventional arts is that each surface of the substrate is flat and smooth. When the substrate is packaged and fastened by the package member, a plane-to-plane contact relation is formed. The plane-to-plane contact provides very little friction between the package member and the substrate, so occurrences of unstable sliding may take place. The mentioned unstable sliding may also take place on the lead frame. Moreover, the package member often utilizes a liquid material for covering the periphery of the substrate or other components to be covered. When the liquid material is solidified for packaging the substrate, the liquid material is hard to be evenly distributed on each surface of the substrate duo to the over smoothness of each surface. One solution adopted is to provide additional amount of material or to manually process the package, thereby consuming unnecessary costs.
Another disadvantage of conventional arts is that the lens cover may not be fastened on the light reflector in a long term. Because the material of the lens cover is plastic, and the light reflector often adopted a metal material for coating a metal layer on the surface so as to increase the reflectivity of the light reflector. It is known that plastic is hard to be adhered and fastened on the surface of a metal, so the plastic-made lens cover may gradually loosen from the metal-made light reflector.
When a loosening situation happens between the substrate and the package member, and when the lens cover is not able to be firmly fastened on the optical lens, moisture or vapor may permeate into the interior of the package structure, thereby deteriorating or even damaging the light emitting component and optical component. As a result, the conventional arts can not be used in a humid environment. Thus, an improved package structure of LED capable of completely blocking vapor and moisture, durable in use, and maintaining the performance of optical component in long term shall be provided.